An electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2014-53765 and an electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2014-230278 are examples of electronic components of the related art.
In the electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2014-53765, first and second capacitor electrodes are provided above first and second coils that form a common mode filter. Third and fourth capacitor electrodes are provided below the first and second coils. The first capacitor electrode and the third capacitor electrode are connected to the two ends of the first coil. The second capacitor electrode and the fourth capacitor electrode are connected to the two ends of the second coil.
A first ground electrode is provided above the first and second capacitor electrodes. A second ground electrode is provided below the third and fourth capacitor electrodes. Capacitances are generated between the first capacitor electrode and the first ground electrode and between the second capacitor electrode and the first ground electrode. Capacitances are generated between the third capacitor electrode and the second ground electrode and between the fourth capacitor electrode and the second ground electrode.
As illustrated in the equivalent circuit of FIG. 9, a first capacitor electrode 131 and a third capacitor electrode 133 are connected to the two ends of a first coil 121, and a first ground electrode 141 faces the first capacitor electrode 131 and the third capacitor electrode 133. A second capacitor electrode 132 and a fourth capacitor electrode 134 are connected to the two ends of a second coil 122, and a second ground electrode 142 faces the second capacitor electrode 132 and the fourth capacitor electrode 134. In other words, a so-called π-type LC filter structure is formed as an equivalent circuit.
On the other hand, the electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2014-230278 includes first to fourth coils that are sequentially arranged in a stacking direction. The first coil and the third coil are connected to each other through a via conductor and form a primary coil. The second coil and the fourth coil are connected to each other through a via conductor and form a secondary coil. A ground electrode is provided between the second coil and the third coil and capacitances are generated between the ground electrode and the primary and secondary coils.
However, when the above-described electronic components of the related art were manufactured and actually used, the following problems were discovered.
In the electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2014-53765, since an π-type LC filter structure is adopted, it is necessary to have large capacitance in order to realize LC resonance. Consequently, a signal transmission characteristic Sdd21 is poor and signal quality is degraded.
On the other hand, in the electronic component disclosed in Japanese Unexamined Patent Application Publication No. 2014-230278, a ground electrode is arranged between the second coil and the third coil and therefore the ground electrode and a via conductor that have different potentials are located in the same layer. Consequently, electrochemical migration occurs due to the potential difference between the ground electrode and the primary and secondary coils (via conductor).